Preheat the oven: Set oven to 325°F (163°C). Grease and flour a 10-inch bundt or tube pan well so the cake doesn’t stick.
Cream the butter and sugar: In a large bowl, beat softened butter and sugar on medium speed for 4–5 minutes, until light and fluffy.
Add eggs and flavorings: Beat in eggs one at a time. Stir in lemon zest, lemon juice, and vanilla extract.
Mix dry ingredients: In another bowl, whisk together flour, baking soda, and salt.
Combine wet and dry: Add flour mixture in three parts, alternating with buttermilk. Start and end with flour. Mix just until blended.
Bake the cake: Pour batter into the prepared pan and smooth the top. Bake for 60–70 minutes, or until a toothpick comes out clean.
Cool the cake: Let it rest in the pan for 15 minutes, then carefully turn it out onto a wire rack. Cool completely before glazing.
Make the lemon glaze: Whisk powdered sugar with lemon juice until smooth and pourable. Adjust consistency with more sugar or juice as needed.
Glaze the cake: Drizzle glaze over the cooled cake. Let it drip down the sides. Sprinkle extra lemon zest on top, if desired.